1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to pistons and their method of construction.
2. Related Art
Engine manufacturers are encountering increasing demands to improve engine efficiencies and performance, including, but not limited to, improving fuel economy, improving fuel combustion, reducing oil consumption, and increasing the exhaust temperature for subsequent use of the heat within the vehicle. In order to achieve these goals, the engine running temperature in the combustion chamber needs to be increased. However, while desirable to increase the temperature within the combustion chamber, it remains necessary to maintain the piston at a workable temperature. As such, it is known to incorporate outer and inner cooling galleries, both open and closed, within the piston head through which engine oil is circulated to reduce the operating temperature of the piston head. The outer cooling galleries typically circulate about an upper land of the piston including a ring groove region while the inner cooling gallery is typically beneath an upper combustion surface of the piston head, commonly referred to as undercrown, which commonly includes a recessed combustion bowl. As such, both the ring belt region and the combustion surface benefit from cooling action of the circulated oil. Wherein a closed cooling gallery is provided, it is known to cast closed cooling galleries; however, the manufacturing process tends to be costly.
A piston constructed in accordance with this invention overcomes the aforementioned disadvantages associated with pistons having a closed cooling gallery.